Efficient, reliable, and real-time communication with minimal latency is a critical requirement for public safety organizations and first responders. Toward that end, the Telecommunications Industry Association (TIA) adopted and standardized a suite of Land Mobile Radio (LMR) standards termed Project 25 (P25), as described for example, in the TIA 102-series documents. The P25 standard defines the operation and interfaces of P25-compliant narrowband radio systems. Additionally, through a gateway, non-P25 compliant radio systems, such as broadband cellular networks, can also interoperate with P25 networks. As used herein, the terms “P25” and “APCO 25” are used interchangeably.
As one example, portable radio transceivers or “walkie-talkies” are often operated within a narrowband P25 network to quickly establish one-to-one and one-to-many communication links. Such radio transceivers are indispensable for law enforcement, rescue, and military personnel, and have even become commonplace across various business environments as well as for recreational activities. In particular, radio transceivers can provide a near instantaneous connection between users in a talkgroup by utilizing push-to-talk (PTT) communications over a half-duplex radio transmission system.
Advances in cellular packet-switched networks have resulted in the development of a broadband push-to-talk over cellular (PoC) service, for example, as described in PoC V1.0.3 Enabler Package released September 2009 by Open Mobile Alliance (OMA), which is hereinafter referred to as OMA PoC. Specifically, an OMA PoC network provides a half-duplex Voice Over Internet Protocol (VoIP) solution, with well-known PTT functionality. OMA PoC is implemented using a Session Initiation Protocol/Internet Protocol (SIP/IP) core. More particularly, OMA PoC employs infrastructure components (also referred to herein as the SIP/IP core) that operate using familiar protocols for voice and control signaling, including Real-Time Transport Protocol (RTP), as described, for example, in Request for Comments (RFC) 3550 dated July 2003 by Internet Engineering Task Force (IETF) and any subsequent revisions, and SIP, for example, as described in RFC 3261 published June 2002 by IETF Network Working Group and any subsequent revisions.
Moreover, broadband cellular networks have continued to improve, for example, with the introduction of 3GPP Long Term Evolution (LTE), as described in the 3GPP 36-series documents and any subsequent revisions. Specifically, LTE networks are designed to offer low latency and high throughput, enabling reliable IP-based streaming of video and other multimedia services. As broadband cellular networks experience greater deployment, it is often desirable for such broadband networks to reliably interface with legacy narrowband networks.
In one example, public safety organizations and first responders use narrowband systems for voice communication while utilizing a complementary broadband cellular network to enable data-intensive multimedia communication. Thus, it may be desirable to extend voice communication, such as PTT communication, from the narrowband network to the broadband network. In another example, enhancement of a broadband PTT service is facilitated by extending the broadband PTT services to include the PTT functionality provided by the narrowband system. However, the extension of such features between two different (and in some cases disparate, i.e., dissimilar and distinct in kind) communication networks should be accomplished in such a way so as to maintain a reliable link between the disparate networks while also maintaining the latency and throughput benefits afforded by the broadband network.
Accordingly, there is a need for a system and method of providing service to a mobile device in a communication network.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required.
Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.